Re: Si-32

[Karin Gordon <kgordon@cc.UManitoba.CA>]

Silicon-32 is an interesting radioisotope.   It is a pure beta emitter with an E-max of 
225 keV and half-life of 104 years.  It decays to P-32 (1.7 MeV e-max, 14.2 day T1/2). 
I first encountered the Si-32/P-32 parent/progeny combination last year when perusing 
the sealed source catalogue issued by Isotope Products Laboratories (a California 
based company).  IPL manufactures sealed disc and planar standard radioisotope sources.
I purchased a Si-32/P-32 disc source to add to my lab's collection of calibrated 
radioisotope sources.  I use these to determine the detection efficiency (counts/second 
per disintegration) of all instruments used for contamination monitoring by our 
teaching hospital nuclear medicine, radiopharmacy and biomedical research laboratories. 

The Si-32/P-32 activity on the IPL disc source is covered with a 0.051 mm Al window, 
which absorbs <60% of the Si-32 225 keV betas, and less than 5% of the P-32 1.7 MeV 
emissions.  Voila - a constant known activity source of P-32, great for instrument 
calibration. BTW, I inquired and IPL can provide planar sources of this isotope in 
different configurations.  I don't know if this radioisotope is available from any 
other vendor of calibrated sources. 

How does your researcher propose to use the Si-32 radioisotope?   Does s/he really 
require a long-lived source of 1.7 MeV beta emissions?  I'd be somewhat concerned if 
this material was to be used as a tracer of some type - because storage/waste disposal 
of this radioisotope with its 104 year half-life and high energy progeny beta emission 
would be problematic. 

I'm responding via rad-safe because I thought many of our RSO colleagues might be 
interested in this radioisotope for instrument calibration purposes. I'm not aware it 
has been used for other applications or of its availability.

Cheerio from the frozen Canadian northland (-29 C this morning).  Happy Thanksgiving to 
my Yankee friends.

Karin Gordon
Radiation Safety Office 	phone 	(204) 787-2903
Health Sciences Centre		fax	(204) 787-1313
Winnipeg, Manitoba, Canada   	e-mail  kgordon@cc.umanitoba.ca



spike@hpel.cees.edu wrote:
> 
> Has anyone used Si-32?  I have an investigator that is interested in a new
> protocol using Si-32.  Any pros, cons, and precautions would be appreciated.
> Please respond directly to me: spike@hpel.cees.edu.
> 
> Thanks in advance.
> Sherry